Go-github: Add Topics API Preview

[gkze]

This would be a very small change, adding application/vnd.github.mercy-preview+json (mediaTypeTopicsPreview) to activity_star.go and would allow the client to get topics for a starred repository.

[gmlewis]

Thank you, @gkze, but could you please be more specific?

I'm looking through the GitHub Developer API docs here:
https://developer.github.com/v3/activity/starring/
and don't see any mention of this custom header.

[gkze]

Sure, this feature was introduced a year ago: https://developer.github.com/changes/2017-07-17-update-topics-on-repositories/ and also works on user/starred, but this seems to be unclear / undocumented.

It seems to only be documented in the "Repositories" section: https://developer.github.com/v3/repos/#list-all-topics-for-a-repository

[gmlewis]

OK, so if I understand you correctly, adding the mediaTypeTopicsPreview custom header to the following endpoint~s~ will return the topics for the starred repo:

• ActivityService.ListStarred
  ~* ActivityService.IsStarred~
  ~* ActivityService.Star~
  ~* ActivityService.Unstar~

correct?
Edit: Striked out incorrect ones.

[gkze]

No - this header should only be passed in ActivityService.ListStarred as the rest of the calls do not return that data.

[gmlewis]

To all:

This would be a great PR for any new contributor to this repo or a new Go developer.
All contributions are greatly appreciated!

Feel free to volunteer for any issue, and we can send you an invite to contribute to the repo (which you then accept after you enable two-factor authentication) and the issue can be assigned to you so that others don't attempt to duplicate the work.

Please check out our CONTRIBUTING.md guide to get started.

Thank you!

[gkze]

I would like to volunteer for this issue.